Traditional soldering processes place a solder pad sandwiched between components to be bonded. During solder reflow the solder melts and spreads out. The surface tension of the melted solder exerts lateral pulling forces on the top component or chip. In most cases the forces are not balanced, and as a result the top component is shifted away from its original aligned position.
As a result of this component shifting during soldering, attaching a laser diode to a slider with sub-micrometer accuracy is a challenging process. The state-of-art chip bonders can achieve the pre-bonding alignment accuracy required, but the post bond alignment usually deteriorates due to the skidding of the parts caused by reflowing of the solder sandwiched between the parts. As such, the best bonding processes for high alignment accuracy are typically those which do not involve a liquid phase of the bonder. However, due to process temperature constraints and requirements for thermal and electrical conduction, non-liquid phase solder is not very feasible and low temperature solder is therefore currently the preferred choice for attaching a laser to a slider in an energy assisted magnetic recording (EAMR) type application. Therefore, an improved solder pad design and corresponding soldering process need to be developed to ensure the post bond alignment accuracy.